[aprssig] APRS-IS core Servers

Tom Hayward esarfl at gmail.com
Thu Aug 16 20:35:30 EDT 2018

On Thu, Aug 16, 2018 at 2:34 PM Steve Dimse <steve at dimse.com> wrote:

> > Could someone tell me what the APRS core servers are needed for?
> > On the websites of some core servers I saw that some people connect to
> them instead of connecting there stations
> > to Tier2 servers. But I think they could switch to Tier2 servers easily.
> >
> This question will open old wounds and probably start a few arguments, but
> here we go.
> The question you should ask is "Why Tier 2?"

Well, it's clear which side Steve is on.

The current Tier2 design was implemented during a period when there were
often no free slots. I believe there were only three or four core servers
at the time and each had a max connection limit of around 200. There were
more than 600 hams/igates on APRS at the time (I believe the total was
around 2k), so at peak times there would be no free slots to connect. By
implementing "hubs" in Tier2, the Tier2 servers could continue to exchange
packets even if they could not connect to core.

Since then, more core servers have been deployed, and many have had their
max connection limits increased (due to more capable hardware and more
efficient software).

Another nice feature about Tier2 is that the rotate addresses are
dynamically built with input from healthchecks. They only include the best
8 servers at the time, and servers are frequently swapped in and out of the
list due to number of free slots, downtime, or increased latency.

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